Shipping containers are used to ship bulk or bagged agricultural commodities. However, four main problems remain unsolved: a) effects of oxidation including generation of free fatty acids (FFAs) where applicable; b) insect infestation and infestation development which can adversely effect quality preservation, c) growth of molds and resulting toxins, and d) raising of moisture content or condensation during trans-shipment. Insect infestation that disqualifies the product quality is a common problem to all packed commodities in polypropylene or jute woven bags, plastic or paper packages. These packaging materials cannot protect the commodities from damage due to “penetrators,” which are insects that can bore holes through packaging materials; and “invaders,” which are insects that enter packages through existing holes, such as folds and seams and air vents. Stored product insects are mainly of tropical and sub-tropical origin, and have spread to temperate areas via international trade. Therefore, it is important to protect the commodities from insect infestation. One method of providing an environmentally sound method of insect control is through hermetic storage.
In order to provide hermetic storage within a shipping container, it is necessary to provide a gastight structure to be placed within the container, and to develop suitable means of holding the gastight structure in place during loading, keeping it open during loading, and hermetically sealing it simply and efficiently. One problem that occurs during shipment is when moisture translocates from the commodity to the upper layers of the stack inside the containers. This moisture migration is caused due to differences in temperature, i.e., gradients, between the metal surfaces of the containers that absorb energy when exposed to solar irradiation and the container headspace with significantly lower temperatures at cooler times of the day. During heat absorption, the headspace of the container adjusts with the equilibrium air relative humidity of the commodity. During the cooler periods of the day, the air moisture at the headspace of the container condenses over the commodity and thereby increases the moisture content of the commodity. This excessive moisture causes mold damage that leads to the production of mycotoxins. In addition, increase in moisture content from outside humidity causes increase in fatty acids, and changes in color, taste and aroma of the commodities that disqualify the products.
The prevention of both condensation and increases in moisture content are important aspects of commodity transportation in containers. One known method of prevention is to provide a modified atmosphere for the agricultural commodity itself and any insects inside the commodity through their respiration. In addition, when useful, the generation of a modified atmosphere may be accelerated by injection of an inert gas. Although use of hermetic storage to preserve agricultural commodities in fixed locations is described in Israeli Patent number 87301, U.S. Pat. No. 6,609,354 and in U.S. Pat. No. 6,941,727 and U.S. patent application Ser. No. 11/970,173, entitled “Ultra-low permeability Lightweight Bunker Storage System and Method,” and in transportable form as described in U.S. patent application Ser. No. 11/368,803, entitled “Flexible Ultra-low Permeability Transport System and Method,” the need to provide a practical hermetic storage for an entire load during transport in conventional shipping containers is unmet.
What is needed is a system and method for protected transportation of agricultural commodities to preserve quality and prevent increases in moisture content of the commodity or moisture damage including condensation that may occur during shipping in containers.